Accurate knowledge of the BECO time is important in obtaining the estimation of the impact point of a ballistic missile. Prior to the present invention, BECO time was estimated by means of an infrared sensor system, which estimated the BECO time from termination of infrared radiation from the missile above a selected threshold. This technique of estimating the BECO time was subject to significant error caused by residual heat in the missile. Error in the BECO time leads to error in the BECO position and velocity and ultimately leads to an error in the estimated impact point.